Page 511 - ACCCN's Critical Care Nursing

488 P R I N C I P L E S A N D P R A C T I C E O F C R I T I C A L C A R E

adequate circulating volume is assured by initial fluid RRT urgent and mandatory. Combined derangements
resuscitation) and haemodynamics, encouraging diuresis can create the necessity to commence therapy before
if present, monitoring blood profiles for changes in urea individually-defined limits have been reached. Early ini-
and electrolytes, and limiting or reformulating the tiation of treatment is widely advocated and may confer
adminis tration of agents that may contribute to the accu- more rapid renal recovery.
mulation of urea and electrolytes (e.g. enteral or IV nutri-
tional supplements). The use of agents such as mannitol, RENAL DIALYSIS
dopamine and frusemide, while popular in practice, have
not been shown to be of any value in improving outcome Despite its complex physiology, human kidney function
in patients at risk of ARF. 13,20 is able to be largely replaced with a management program
that includes an artificial process of RRT that can sustain
Despite these efforts, life-threatening biochemistry may individuals for many years in the community setting. In
arise in ARF, such as severe acidosis and hyperkalaemia critically ill patients with ARF, this program focuses pre-
(a pH of <7.1 and a serum potassium >6.5 mmol/L) that dominantly on RRT, rather than on the endocrine func-
requires immediate treatment and can be an indication tions of the kidney.
for beginning RRT without elevation of serum creatinine
and oliguria and fluid overload. 33 HISTORY
Dialysis is a term describing RRT and refers to the purifi-
NUTRITION cation of blood through a membrane by diffusion of
36
When ARF is persistent, providing nutritional support waste substances. Table 18.1 outlines the historical
is another important management strategy. A review events in the development of dialysis. The Kolff rotating
of nutrition in ARF suggested that an intake of 30–35 drum kidney, one of the earliest attempts at RRT (illus-
kcal/kg/day and a protein intake of 1–2 g/kg/day is essen- trated in Figure 18.8), used cellulose tubing rolled around
tial due to the combined increase in protein catabolism a wooden skeleton built as a large, drum-styled cage. Cel-
34
and caloric requirements of associated critical illness. lulose acetate (material similar to ‘sticky tape’) tubing was
This nutrition is provided by the enteral or parenteral strong, did not burst under pressure and could be steril-
37
route and constitutes an increase in body fluids and nitro- ised. The drum with the blood-filled cellulose tubing
gen load. Ironically, this aspect of managing ARF in criti- wound around it was immersed in a bath of weak salt
35
cal illness may also be an indication for starting RRT solution, and as blood passed through, the rotating cel-
(see Chapter 19 for further discussion on nutritional lulose tubing allowed waste exchange to occur by diffu-
requirements in critical illness). sion. This method and the diagram included is useful
information as it is essentially the key concepts for how
RENAL REPLACEMENT THERAPY

If conservative measures fail, then the ongoing manage-
ment of the patient with ARF requires RRT. This enables
control of blood biochemistry, prevents toxin accumula-
tion, and allows removal of fluids so that adequate nutri-
tion can be achieved. The criteria and indications for
initiating RRT are listed in Box 18.1. One indication
is sufficient to initiate RRT, while two or more make

BOX 18.1 Proposed criteria for the initiation
of renal replacement therapy in adult
critically ill patients 14

● Oliguria (urine output <200 mL/12 h)
● Anuria/extreme oliguria (urine output <50 mL/12 h)
+
● Hyperkalaemia (K >6.5 mmol/L)
● Severe acidaemia (pH < 7.1)
● Azotaemia (urea > 30 mmol/L)
● Clinically significant organ (esp. lung) oedema
● Uraemic encephalopathy
● Uraemic pericarditis
● Uraemic neuropathy/myopathy
+
● Severe dysnatraemia (Na >160 or <115 mmol/L)
● Hyperthermia
● Drug overdose with dialysable toxin
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FIGURE 18.8 Kolff dialyser.